Needle positioning apparatus for stitching machines

ABSTRACT

Apparatus for positioning the needle of a stitching machine in a preselected position along its reciprocatory path including a pneumatically powered positioning motor connected to the drive shaft for the needle, a source of pressurized fluid (preferably air), conduit means connecting the source of pressurized fluid to the positioning motor, normally closed valve means interposed in the conduit means and control means also interposed in the conduit means at a location between the valve means and the positioning motor and adaptable to activate and deactivate the motor for positioning the needle.

United States Patent 1191 Tice [ Dec. 9, 1975 [54] NEEDLE POSITIONING APPARATUS FOR STITCHING MACHINES [76] Inventor: William A. Tice, 6675 Maynardville Highway, Knoxville, Tenn. 37918 22 Filed: Sept. 9, 1974 21 Appl. No.: 504,324

[52] US. Cl. 112/219 B; 112/252 [51] Int. Cl. DOSB 69/22; DOSB 65/02 [58] Field of Search 112/219 B, 219 A, 219 R,

[56] References Cited UNITED STATES PATENTS 3,592,153 7/1971 Margereson .1 112/219 B FOREIGN PATENTS OR APPLICATIONS' 497,893 12/1938 United Kingdom 112/219 B Primary Examiner-H. Hampton Hunter Attorney, Agent, or FirmFitch, Even, Tabin & Luedeka [5 '7 ABSTRACT Apparatus for positioning the needle of a stitching machine in a preselected position along its reciprocatory path including a pneumatically powered positioning motor connected to the drive shaft for the needle, a source of pressurized fluid (preferably air), conduit means connecting the source of pressurized fluid to the positioning motor, normally closed valve means interposed in the conduit means and control means 1 also interposed in the conduit means at a location between the valve means and the positioning motor and adaptable to activate and deactivate the motor for positioning the needle.

13 Claims, 5 Drawing Figures AIR SUPPLY AIR FILTER 'U.s. Patent Dec.91975 Sheetl0f4 3,924,553

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U.S. Patent Dec. 9 1975 Sheet 2 of4 3,924,553

BRAKE-CLUTCH 44 ASSEMBLY AIR -32 SUPPLY U.S. Patent Dec. 9 1975 Sheet 3 of 4 3,924,553

36 BELT TO DRIVE MOTOR Fig.3

U.S. Patant Dec. 9 1975 Sheet 4 of4 3,924,553

NEEDLE POSITIONING APPARATUS FOR STITCIIING MACHINES This invention relates to stitching machines and more particularly to apparatus for positioning the reciprocatable needle of such machines in a predetermined position along the reciprocatory path.

It is well recognized in the industries which use stitching machines, particularly the garment industry, that there exists a need for apparatus associated with a stitching machine which will position the reciprocatory needle either in the work or out of the work upon the completion of a stitching operation. Such positioning of the needle at the end of a stitching operation has been performed heretofore by the operator turning a hand wheel to rotate the drive shaft for the needle to move the needle into or out of the work as desired.- By way of example, if the work-piece is to be turned to change the direction of stitching, it is desired that the needle be stopped in the work. Contrariwise, if the work-piece is to be removed from the machine at the end of the stitching operation, it is desired that the needle be stopped in a position out of the work.

Numerous devices have been proposed for automatically positioning the needle of a stitching machine in a preselected position at the end of a stitching operation. These devices predominately have been of the electrical or electro-mechanical type. In most all instances, these devices have involved the use of a cam or its equivalent associated with the drive shaft for the needle and a cam-follower type mechanism which halts the rotation of the needle drive shaft upon the needle achieving the desired position. Most generally, these prior art devices have each included an auxiliary motor which rotates the needle drive shaft after the main drive motor for the needle drive shaft has been stopped at the end of a stitching operation.

Despite the acknowledged advantages of a needle positioning apparatus, and despite the numerous attempts to accomplish the desired results, it is generally acknowledged in the industry that there are no needle positioning devices presently available that are satisfactory from either their operation and/or economic standpoints. Besetting these prior art needle position devices are the problems of complexity of design, difficulty of installation, and sensitivity to maladjustment, all of which contribute to relatively high initial cost and inordinate demands relating to maintenance of the de vices after their installation. So far as is known to applicant, heretofore there has been no pneumatically operated needle positioning device.

It is an object of this invention to provide apparatus for automatically positioning the needle of a stitching machine in a preselected position at the end of a stitching operation. It is another object to provide a needle positioning apparatus which is pneumatically operated. It is another object of this invention to provide a novel control system for use in apparatus for performing an auxiliary function of a stitching machine. It is another object to provide apparatus employing pneumatic power for automatically positioning the needle of a stitching machine and to perform one or more additional functions relating to the stitching operation. Other objects and advantages of this invention will be recognized from the following description, including the drawings, in which:

FIG. 1 is a representation of a stitching machine including apparatus depicting various features of the invention;

FIG. 2 is a representation of one embodiment of an operator control device for activating operation of the disclosed apparatus;

FIG. 3 is a rear elevational view of a portion of the disclosed apparatus; and

FIGS. 4 and 5 are sectional views, partly fragmentary, of a piston-cylinder, detent and cam arrangements embodied in the disclosed apparatus;

Briefly stated, the present invention comprises apparatus for positioning the needle of a stitching machine in a preselected position along its reciprocatory path including a pneumatically powered positioning motor connected to the drive shaft for the needle, a source of pressurized fluid, conduit means connecting the source of pressurized fluid to the positioning motor, valve means interposed in the conduit means, and control means also interposed in the conduit means at a location between the valve means and the positioning motor and adapted to activate and deactivate the motor for positioning the needle. This apparatus is fitted on a conventional stitching machine 10 and cooperates therewith such that when an operator stops the stitching machine upon the completion of a stitching operation, pressurized air, or its equivalent, is admitted through a normally closed valve 12 to a piston-cylinder control device 14. The position of the piston member 16 (FIG. 5) within the cylinder member 18 establishes the flow of pressurized fluid to a positioning air motor 20 (FIG. 3) that is drivingly connected to the drive shaft 22 for a reciprocatory needle 24. Cam means 26 fitted on the drive shaft 22 adjacent a detent means 28 connected to the piston member 16 functions cooperatively with the pressurized fluid and biasing means, e.g. spring 30 (FIG. 5), to establish the piston of the piston member within the cylinder member, hence to determine activation and deactivation of the air motor.

With reference to FIG. 1, the depicted apparatus includes a source of pressurized fluid 32 connected through a conduit 34, the normally closed valve 12 and through a control system indicated generally at 14, to the air motor 20, which is drivingly connected to the drive shaft 22 whose rotation moves the needle 24 along its reciprocatory path.

In FIG. 1, there is depicted in phantom a stitching machine 10 including a table 36, a machine frame 38 mounted on the top surface 40 of the table, main drive motor means 42 mounted on the underside of the table, conventional clutch and brake means 44 also mounted on the underside of the table and including linkage means 46 operatively connecting the brake and clutch means to a treadle 48. The stitching machine further includes a work support 50 hingedly connected at 52 to the table 36 for movement in generally up and down directions to hold a workpiece in position beneath the needle 24 for performance of a stitching operation thereon. The needle 24, in the depicted embodiment, is mounted on an arm 54 for reciprocation along an arcuate path as indicated generally by the arrow A of FIG. 1. The arm 24 is reciprocated by means of a shaft 56 attached by a wobble mechanism 58 to the main drive shaft 22 of the machine. This main drive shaft 22 extends from the frame 38 to receive thereon a drive pulley 60 fixed on to the shaft 22 by an overriding clutch of conventional design. This drive pulley is drivingly connected by a belt 62 to a further pulley 64 mounted beneath the table 36 and operatively engageable with the motor 42 by a brake-clutch mechanism 44 for rotation of the drive shaft and reciprocation of the needle when the drive motor is engaged. The belt 62 passes upwardly through an opening 66 in the table 36 As noted above, the position of the needle 24 along its reciprocatory path is established by a pneumatically operated control system comprising a source of pressurized fluid 32, preferably air, which is fed through the conduit 34 and an air filter 68 to the inlet 70 of the normally closed valve 12 (FIGS. 1 and 2). One suitable valve comprises a Model MJV-3 valve available from the Clippard Valve Company, Cincinnati, Ohio. In the depicted embodiment this valve 12 is mounted on a first block 80 which is fixedly secured as by a set screw 82 to a first pitman rod 84 as will be referred to further hereinafter.

The valve 12 is provided with a plunger 86 having an exhaust port 88 therein, disposed adjacent a second block 90 that is fixedly secured as by a set screw 92 to a second pitman rod 94 connected at one of its ends 96 to the treadle 48 hingedly mounted for movement by an operators foot, and extending upwardly therefrom. This second block 90 is disposed below the first block 80 and the pitman rods are in generally parallel alignment so that the vertical movement of the pitman rods relative to each other results in relative movement between the first and second blocks 80 and 90 and resultant opening and closing of the valve 12 by reason of the second block 90 operatively contacting the plunger 86 of the valve 12. The first and second blocks 80 and 90 are biased in spaced apart relation and toward a position of nonoperative engagement of the second block with the plunger 86 by a spring 98. The position of the second block 90 along the length of the second pitman rod 94 is chosen such that when the foot treadle 48 is in its up position, the block will be either out of contact or in nonoperative contact with the plunger 86 of the valve 12 so that the valve remains closed. The second pitman rod 94 is provided with a further block 100 which is fixedly secured to the pitman rod as by a set screw 102. This further block is disposed above the first block 80 and functions to limit the upward travel of the first block 80 and thereby maintain the position of the plunger 86 with respect to the second block 90. Upon depression of the foot treadle, the second pitman rod is pulled downwardly causing the further block 100 to bear against the first block 80 and urge the plunger 86 of the valve 12 downwardly into operative engagement with the second block 90 to open the valve 12. Simultaneously, the depression of the foot pedal functions to also lower the first pitman rod 84 and activate the drive motor 42 as by the medium of the conventional brake and clutch mechanism 44. When the valve 12 is closed, pressurized fluid downstream thereof is exhausted through exhaust port 88 in the plunger 86.

The outlet 106 of the valve 12 is connected by a conduit 108 to an inlet 110 (FIGS. 3 and 4) to the cylinder portion 18 of the piston-cylinder member 14. As depicted in FIGS. 1, 3, 4 and 5, the cylinder member 18 is provided with an outlet 112 that is connected by a conduit 114 to the air motor 20 mounted on the underside of a mounting plate 1 16 which is secured to the top surface 118 of the machine frame 38. The air motor 20 is drivingly connected to a pulley 120 fixed on the main drive shaft 22 employing a conventional overriding clutch of the type referred to hereinbefore, employing belt means 122 trained about a pulley 124 mounted on a shaft 126 mounted on a gearbox 128.

Referring to FIGS. 1 and 3, in one embodiment, the air motor 20 includes a shaft 130 fitted with a first gear 132. This first gear 132 meshes with a second gear 134 that is fitted on the shaftl26 journaled in the wall 138 of the gear box 128, and extending exteriorly thereof to receive the pulley 124thereon. As noted, the pulley 124 is drivingly connected to the pulley 120 provided on the main drive shaft 22 of the stitching machine, as by a continuous loop belt 122 that is trained about these pulleys. By this apparatus, including the overriding clutch feature, of the pulley 120, the air motor functions to rotate the drive shaft 22 when the air motor is activated. The pulley 120 coasts when the air motor is inactivated and the main drive motor 42 is activated to perform a stitching operation.

The main drive shaft 22 of the stitching machine is provided at its outboard end with the cam 26 which has a peripheral recess 142 therein. As seen in FIGS. 1, 4 and 5, the piston-cylinder member 14 includes a piston member 16 having a rod 144 connected to one end 146 thereof. The opposite end 148 is threaded to receive a hub 150 of a low-friction material, such as polytetrafluoroethylene, to define a detent adapted to engage the peripheral surface 152 of the cam 26 and at an appropriate time, to substantially enter the recess 142 in the cam surface. The piston-cylinder member 14 is also mounted on the underside of the mounting plate 116 to position the detent relative to the cam. As shown in FIG. 1, the relative position of the mounting plate 116 with respect to the machine frame 38, the relative position of the piston-cylinder member 14 with respect to the mounting plate 116, and a mounting bracket 156 for the piston-cylinder are variable as by means of bolts 158, 160 and 162, which may be positioned at desired locations within respective elongated slots through which the bolts pass.

In the depicted embodiment, the piston-cylinder member 14 includes a second outlet which is connected by a conduit 172 to a pulse valve 171, thence by a conduit 173 to the cylinder 182 of a second pistoncylinder means 174 mounted as by a bracket 176 on the underside of the table 36. The piston element 178 of the second piston-cylinder device passes upwardly through an opening 180 in the table to pivotally engage the hinged work support 50 such that retraction of the piston 178 into the cylinder 182 functions to lower the work support 50 and release a workpiece for removal from the stitching machine. The pulse valve 171 is further connected by a conduit 175 to the cylinder 177 of a thread cutter 179 that is mounted on the machine frame as by a bracket 181.

Referring to FIGS. 1, 3, 4 and 5, the control system comprises the piston-cylinder member 14, the cylinder portion 18 of which is adjustably mounted on the lower side of the mounting plate 116, as noted above. Referring to FIGS. 4 and 5, this cylinder member 18 is provided with a bore 186, the inlet end 110 of which is internally threaded for connection of the conduit 108 thereto. The cylinder is further provided with a lateral passageway 188 leading from the bore through the internally threaded outlet 1 12 to the exterior of the cylinder. In the depicted embodiment, the cylinder 18 is provided with a further lateral passageway 190 which leads from'the bore to the exterior of the cylinder. Similarly, this passageway is provided with a threaded outlet 170 for connecting the conduit 172 thereto.

The piston 16 is slidably received within the bore 186 of the cylinder 18. This piston is biased as by the spring 30, toward the inlet end 110 of the bore 186. On that end of the piston opposite the inlet end to the cylinder, there is provided the rod 144 whose outboard end is provided with the detent referred to above. This detent is positioned such that movement of the piston within the cylinder causes the detent to move between positions of engagement and disengagement with the pheripheral surface 152 of the cam 26 and in appropriate circumstances to enter the recess 142 in the cam periphery.

In accordance with the present invention, the movement of the piston 16 against the biasing force of the spring 30 is accomplished by applying pressurized fluid, air for example, through the inlet end of the cylinder 18 such that a force is exerted against the exposed end 200 of the piston 16 to urge the piston to the left as viewed in FIGS. 4 and 5 to move the detent into engagement with the cam 26.

As seen in FIGS. 4 and 5, the piston 16 is provided with an axial passageway 202 leading from the exposed end 200 of the piston inwardly of the piston. The piston is further provided with lateral passageways 204, 206, 208 and 210 (passageway 210 is not visible in the FIG- URES but is located 180 degrees from passageway 208), which communicate between the first passageway 202 and the exterior of the piston (hence communicating with the bore 186 of the cylinder). Seal means, such as 0 rings 212 and 214, encircle the piston member at locations adjacent to and on opposite sides of the exit ports of the lateral passageways 204, 206, 208 and 210. In the depicted embodiment, the external diameter of the piston is reduced in the region between the seals 212 and 214 to define an annular cavity or chamber 216 between the piston and the internal wall of the bore 186. Further seal means such as O ring 218 is provided adjacent the exposed end of the piston and nearer such exposed end than the O ring 214, to define a blind annular cavity or chamber 220 between these 0 rings and between the piston and internal wall of the bore.

In one example of a piston-cylinder as depicted in FIG. 4, the bore 186 in the cylinder was 0.375 inch in diameter. The piston was 0.367 inch in diameter except that the diameter of the piston in the region between the 0 rings 212 and 214 was reduced to 0.0346 inch in diameter. In this example, the area of the exposed face of the piston was 0.947 inch, taking into consideration the cross-sectional area of the passageway 202, which was 0.01 l inch The cross-sectional area of each of the lateral passageways 204, 206, 208 and 210 was 0.0046 inch, or a total cross-sectional area of the four passageways of 0.018 inch. Under these conditions, employing an air pressure of 50 pounds per square inch applied through a .4-inch internal diameter conduit, there was an adequate supply of pressurized air supplied to the bore 186 to force sufficient air through the passageway 202 in the piston, thence out through the lateral passageways 204, 206, 208 and 210, thence through the annular cavity 216, thence through the lateral passageway 188 (0.00072 inch cross-sectional area) in the housing, thence through the conduit 114 to the air motor 20 to activate and drive the air motor for rotating the drive shaft 22 of a US. Blind Stitch Machine, Model No. 99 TT, for example. The air passing through the air motor was exhausted through a muffler 222 having an exhaust port 224.

A further feature of the depicted apparatus includes the ability of the apparatus to automatically cut the thread at the needle 24 and lower the work support 50 (termed a frame in certain instances) upon completion of a stitching operation. This is accomplished by introducing, at the appropriate time in the operation of the machine, pressurized air to the cylinder 177 of the thread cutter 179 of conventional design to extend the piston 183 thereof to move a cutting knife 187 into severing engagement with the thread (not shown) and, thereafter, introducing pressurized air to the cylinder 182 mounted on the bracket 176 that is secured to the table 36 to retract the piston 178 into the cylinder 182 to swing the work support down against the force of a spring hinge 52 and out of its position of support for the workpiece. Movement of the piston 178 to its retracted position is accomplished by supplying pressurized fluid to the top end of the cylinder (as viewed in FIG. 1) via a conduit 173.

Referring to FIGS. 4 and 5, it is seen that when the detent means 28 is disposed substantially within the recess 142 of the cam 26, the piston 16 is so positioned within the bore 186 of the cylinder 18 that the annual cavity 216 is disposed adjacent the lateral passageway 190 in the cylinder 18 and pressurized fluid flowing through the axial passageway 202 in the piston flows via conduit 172 to the dual inlets 189 and 191 of the pulse valve 171 (for example, a Model TAC 4P 34AR pulse valve as sold by Humphrey Products, Kalamzoo, Mich.) This valve 171 functions to initially pass the incoming pressurized air out through one of its outlets 193 and after a brief period of time to switch the air from the outlet 193 to a second outlet 195, while at the same time exhausting the pressure downstream to the outlet 193. In the depicted embodiment, the outlet 193 is connected by the conduit 175 to the thread cutter 171 so that initially upon the flow of pressurized air from the control 14 to the pulse valve 171, the air activates the thread cutter to sever the thread. Thereupon, sufficient time has elapsed for the pulse valve 171 to switch the air to the second outlet 195. This outlet 195 is connected via conduit 173 to the cylinder 182 so that the air acts to retract the piston 178 and lower the work support. Upon the switching by the valve 171, the air in the cylinder 177 of the thread cutter 179 exhausts through the valve 171 and allows the piston and the cutting knife to be retracted by a spring (not shown) within the cylinder 177 that biases the piston toward its retracted position. Upon the closing of the valve 12 by the operator working the treadle 48, the pressurized fluid within the cylinder 182 exhausts back through the valve 171 and the conduit 172 into the bore 186, thence through the conduit 108 and the exhaust port 88 of valve 12. After the pressurized fluid has exhausted, the work support moves to its up position under the influence of the spring hinge 52. Further, the piston 16, under the influence of spring 30, returns to its position adjacent the inlet end of the cylinder 18.

In the usual stitching machine, the main drive motor of the machine is activated and operates continuously. Engagement of the drive shaft for reciprocation of the needle is commonly accomplished by means of a conventional brake-clutch mechanism that is activated and/or deactivated by a foot treadle connected to the brake-clutch mechanism. The disclosed apparatus is inoperative at all times when the needle is being reciprocated by reason of the main drive motor being engaged, such inoperative status being assured by the aforedescribed normally closed valve and its mounting relation with the foot treadle. In the disclosed apparatus, pressurized air is supplied to the inlet of the normally closed valve 12 at all times during operation of the stitching machine. When the operator heels the foot treadle to disengage the main drive motor and stop the stitching operation, the plunger 86 of the normally closed valve 12 is moved to open the valve 12 and admit air to the inlet of the cylinder 18. FIG. depicts the general position of the piston 16 within the cylinder 18 at this state of operation of the apparatus. It is to be recognized that the representations in FIGS. 4 and 5 are not to scale and the relative positions of the seals 212, 214 and 218 to one another and the position of the chamber 216 with respect to the passageway 188 are illustrative only. The pressurized air entering the cylinder 18 acts against the end 200 of the piston 16 to overcome the biasing force of the spring to move the piston within the cylinder to a position such that the detent means 28 bears against the circumferential surface 152 of the cam 26. In the depicted embodiment, this movement of the piston is very slight and in any event is such that the piston stops at a location within the bore 186 such that the annular cavity 216 is adjacent to and in communication with the lateral passageway 188 of the cylinder 18 so that substantially immediately upon the introduction of pressurized air to the inlet end of the cylinder 18, such pressurized air flows through the axial passageway of the piston, thence through the annular cavity 216, thence to the air motor 20 to activate this motor to rotate the drive shaft 22, hence rotate the cam 26. As the cam rotates, the detent 28 slides on the circumferential surface of the cam until the recess 142 in the cam surface comes into register with the detent, whereupon the detent moves into the recess by reason of the pressure applied to the exposed end 200 of the piston 16. This action not only applies a braking force to the cam against further rotation thereof, it also causes the piston 16 to move further into the bore 186 and position the annular cavity 216 out of communication with the lateral passageway 188 leading to the air motor and to position the blind annular cavity 220 adjacent such lateral passageway 188 to seal this passageway and deactivate the air motor 20. Of course, when the air motor 20 stops, the rotation of the drive shaft 22 by such motor, hence the rotation of the cam 26, stops.

In mounting the cam 26 on the drive shaft 22, the cam is rotated on the drive shaft and fixedly secured in a position such that when the needle is in its up position (for example), the recess 142 in the cam surface is in register with the detent 28. Thus, when the detent enters the recess and rotation of the cam and drive shaft 22 is stopped, the needle is stopped in its up position (out of the work). When it is desired to stop the needle in its down position, that is, in its position in the work, the cam only need be rotated 180 on the drive shaft 22 and fixed in such rotated position. whereupon, when the recess comes into register with the detent, the needle will be stopped in its down position.

As depicted in the Figures and explained hereinbefore, the present apparatus also includes provision for cutting the thread and lowering the work support 50 of the stitching machine when the machine is stopped with the needle in the desired position and the detent resides in the recess of the cam. These features are advantageous in many stitching machines in that they enhance the speed with which the operator can remove a finished workpiece and insert a new workpiece.

When the operator desires to recommence a stitching operation, the foot treadle is depressed whereupon the second block on the pitman rod 84 moves out of contact with the plunger 86 to close the valve 12 and shut off the pressurized air from the cylinder 18. Thereupon the biasing force of the spring 30 urges the piston 16 toward the inlet end of the cylinder 18. Exhausting of the pressure in the cylinders 182 and 177 occurs as explained hereinabove. Upon movement of the piston 16 to its limit of travel adjacent the inlet end of the cylinder 18 and against one end 228 of a fitting 230 threaded in the inlet end of the cylinder 18, the annular cavity 216 again moves into communication with the lateral passageway 188 to permit exhausting of the pressurized fluid from the air motor through the cylinder 18 into the conduit 108, and eventually through the exhaust port 88 of the plunger 86. The apparatus thus is repositioned for reactivation upon the operator again heeling the foot treadle at the end of a stitching operation.

It is to be noted that in the present apparatus the interrelationship of the several components of the apparatus prevents activating the air motor, hence positioning of the needle, until the operator has stopped the stitching machine at the end of a stitching operation. This is assured by the use of the normally closed valve 12 and its physical relationship to the foot treadle 48. Further, the disclosed apparatus acts positively to perform its needle positioning function without malfunction by reason of the minimum number of moving parts included in the system. Similarly, installation of the apparatus on new or existing machines is simple. It is relatively inexpensive to manufacture and employs only pressurized air to operate, such being commonly available in manufacturing plants using stitching machines. Further, the apparatus is insensitive to maladjustment or deterioration by reason of the usual extended periods of continuous and demanding use to which stitching machines are commonly subjected.

Whereas, a specific embodiment of the apparatus and its operation have been disclosed, it is understood that other embodiments or equivalents will be appparcut to one skilled in the art. For example, one can employ an electric drive motor connected directly (i.e. mechanically) to the needle drive shaft instead of the drive motor disclosed herein and its belt drive connection to the needle drive shaft.

Further, the valve 12 can be positioned adjacent the treadle 48 for opening and closing thereof by reason of its plunger 86 being contacted directly by the treadle. Still further, it is to be understood that the present apparatus is suitable for positioning the needle of many different machines and the depicted and described U.S. BlindStitch machine is by way of example only.

What is claimed is:

1. In a stitching machine including a needle adapted for reciprocatory movement into and out of a workpiece, shaft means connected to said needle for reciprocating said needle upon rotation of said shaft, drive means including a drive motor for rotating said shaft, operator control means for activating and deactivating said drive means, the improvement for positioning said needle in a preselected position along its reciprocatory path comprising a pneumatically powered positioning motor,

9 means connecting said positioning motor in driving relation to said shaft means for rotation of said shaft means when said drive motor is inactive,

a source of pneumatic pressure,

conduit means connecting said source of pneumatic pressure to said positioning motor, valve means interposed in said conduit means and actuatably responsive to functioning of said operator control means,

control means interposed in said conduit means between said valve means and said positioning motor and operative when said valve means is open to activate said positioning motor to rotate said drive shaft to position said needle in a preselected position along its reciprocatory path,

said control means comprising cylinder means having a bore extending therethrough, piston means disposed in said bore and having one of its ends exposed to said pressurized fluid when said valve means is open, the opposite end of said piston means being disposed externally of said cylinder means and defining detent means, cam means having a recess therein and mounted on said drive shaft in juxtaposition to said detent means, means defining a passageway in said piston means from its exposed end to an exit location within said bore, seal means defining a plurality of chambers between said piston means and said cylinder means, at least one of said chambers communicating with said exit location of said passageway in said piston means, and means defining an exit passageway from said bore to the exterior of said cylinder means at a location contiguous to said chambers, whereby the position of said piston means within said bore establishes fluid communication between at least one of said chambers and said exit passageway to control the flow of pressurized fluid to said positioning motor.

2. The improvement of claim 1 including means biasing said piston within said cylinder means toward a position of nonengagement of said detent means with said cam means.

3. The improvement of claim ll wherein the relative positions of said chambers is such that when said detent means bears against said cam means but does not reside substantially in said recess in said cam, said exit passageway is in fluid communication with said source of pressurized fluid and when said detent resides substantially in said recess, said exit passageway is not in fluid communication with said source of pressurized fluid.

4. The improvement of claim 3 wherein said positioning motor is connected to said exit passageway in said cylinder means whereby pressurized fluid flows to said motor for operation thereof when said detent bears against said cam but does not reside substantially in said recess.

5. The improvement of claim 11 and including a further exit passageway in said cylinder means that communicates between said boreand the exterior of said cylinder means, the location of said further exit passageway being such that when said detent resides substantially in said recess in said cam means, that annular chamber that communicates with said exit location of said passageway in said piston means is in communication with said further exit passageway in said cylinder means.

6. The improvement of claim wherein said stitching machine includes a work support hingedly mounted thereon for movement between positions of engagement and nonengagement with a workpiece, said work support being biased toward its position of engagement with said workpiece, and including a pneumatically activated piston-cylinder means whose piston member is connected to said work support and whose cylinder means is connected in fluid communication with said further exit passageway in said cylinder means whereby when said detent resides substantially in said recess in said cam means, pressurized fluid flows to said cylinder means to move said piston means therein and move said work support to its position of nonengagement with said workpiece.

7. The improvement of claim 2 wherein said passage way in said piston means has a cross-sectional area that is smaller than the remainder of the cross-sectional area of that end of said piston means that is exposed to 'said pneumatic pressure whereby the force exerted against said exposed end of said piston means is sufficient to overcome said bias of said piston means and further provide for the flow of pressurized fluid through said passageway to operate said positioning motor.

8. The improvement of claim 1 wherein said passageway in said piston means includes a plurality of exit ports, each of which is of a smaller cross-sectional area than the minimum cross-sectional area of said passageway, and the total of the crosssectional areas of all of said exit ports is greater than said minimum cross-sectional area of said passageway.

9. The improvement of claim 1 wherein said passageway in said piston means includes a portion which ex tends substantially axially along the length of said piston means and a portion which extends substantially laterally from said axial portion and which exits into said bore of said cylinder means.

10. The improvement of claim 1 wherein that end of said piston means disposed adjacent said cam means is provided with a tip member adapted to enhance the functioning of said end as a detent means.

lli. The improvement of claim 1 and including thread cutter means including a piston and cylinder means, knife means mounted on the free end of said piston in position to cut the thread employed with said stitching machine upon actuation of said piston means, conduit means connecting said cylinder means in fluid communication with said further exit passageway from said control cylinder whereby when said detent means resides substantially within said recess in said cam means, said piston is activated to out said thread.

12. The improvement of claim 11 and including time delay flow control means interposed in said conduit between said control cylinder and said thread cutter cylinder means.

13. In a stitching machine including a needle adapted for reciprocatory movement into and out of a workpiece, shaft means connected to said needle for reciprocating said needle upon rotation of said shaft, drive means including a drive motor for rotating said shaft, operator control means for activating and deactivating said drive means, the improvement for positioning said needle in a preselected position along its reciprocatory path comprising pulley means including overriding clutch means fitted on said shaft means,

a pneumatically powered positioning motor,

loop means drivingly connecting said positioning motor to said pulley means for rotating said shaft upon activation of said positioning motor,

cam means disposed on said shaft and rotatable therewith, saidcam means including a recess therein,

pneumatically actuable reciprocatory piston means having one of its ends disposed adjacent said cam means and defining detent means adapted to move between positions of engagement and nonengagement with said cam means, said piston means being biased toward a position of nonengagement of said detent means with said cam means,

cylinder means including bore means adapted to receive said piston means therein for reciprocatory movement of said piston means,

a source of pressurized fluid,

conduit means connecting said source of pressurized fluid to one end of said bore means for supplying pneumatic pressure to one end of said piston means to urge said piston means toward a position of engagement of said detent means with said cam means,

means defining a passageway for the flow of pressurized fluid along said piston means from said one end thereof that is' exposed to said pneumatic pressure to said bore in said housing,

a plurality of seal means encircling said piston means on opposite sides of the exit end of said passageway along said piston means and sealing the annular space between said piston and the internal wall of said bore on opposite sides of said exit end of said passageway to define a first annular chamber,

further seal means encircling said piston means and sealing the annular space between said piston and said bore at a location more near that end of the piston that is exposed to said pneumatic pressure than either of said plurality of seal means and spaced therefrom to define a further annular chamber between said further seal means and the neighboring one of said plurality of seal means,

means defining a lateral passageway in said cylinder means and communicating between said bore and the exterior of said cylinder means,

conduit means connecting said lateral passageway in said cylinder means to said positioning motor for conveying pressurized fluid to said motor for operation thereof,

normally closed valve means interposed in said conduit means connecting said source of pressurized fluid to said cylinder means whereby upon the opening of said valve means pressurized fluid is admitted to said one end of said cylinder means to move said piston means within said bore and cause said detent means to engage said cam means and to admit pressurized fluid to said first chamber, thence to said positioning motor for rotating said drive shaft and said cam means mounted thereon, whereby said detent means substantially enters said recess in said cam and said piston moves within' said bore by an amount sufficient to close off the flow of air to said positioning motor to stop the same. 

1. In a stitching machine including a needle adapted for reciprocatory movement into and out of a workpiece, shaft means connected to said needle for reciprocating said needle upon rotation of said shaft, drive means including a drive motor for rotating said shaft, operator control means for activating and deactivating said drive means, the improvement for positioning said needle in a preselected position along its reciprocatory path comprising a pneumatically powered positioning motor, means connecting said positioning motor in driving relation to said shaft means for rotation of said shaft means when said drive motor is inactive, a source of pneumatic pressure, conduit means connecting said source of pneumatic pressure to said positioning motor, valve means interposed in said conduit means and actuatably responsive to functioning of said operator control means, control means interposed in said conduit means between said valve means and said positioning motor and operative when said valve means is open to activate said positioning motor to rotate said drive shaft to position said needle in a preselected position along its reciprocatory path, said control means comprising cylinder means having a bore extending therethrough, piston means disposed in said bore and having one of its ends exposed to said pressurized fluid when said valve means is open, the opposite end of said piston means being disposed externally of said cylinder means and defining detent means, cam means having a recess therein and mounted on said drive shaft in juxtaposition to said detent means, means defining a passageway in said piston means from its exposed end to an exit location within said bore, seal means defining a plurality of chambers between said piston means and said cylinder means, at least one of said chambers communicating with said exit location of said passageway in said piston means, and means defining an exit passageway from said bore to the exterior of said cylinder means at a location contiguous to said chambers, whereby the position of said piston means within said bore establishes fluid communication between at least one of said chambers and said exit passageway to control the flow of pressurized fluid to said positioning motor.
 2. The improvement of claim 1 including means biasing said piston within said cylinder means toward a position of nonengagement of said detent means with said cam means.
 3. The improvement of claim 1 wherein the relative positions of said chambers is such that when said detent means bears against said cam means but does not reside substantially in said recess in said cam, said exit passageway is in fluid communication with said source of pressurized fluid and when said detent resides substantially in said recess, said exit passageway is not in fluid communication with said source of pressurized fluid.
 4. The Improvement of claim 3 wherein said positioning motor is connected to said exit passageway in said cylinder means whereby pressurized fluid flows to said motor for operation thereof when said detent bears against said cam but does not reside substantially in said recess.
 5. The improvement of claim 1 and including a further exit passageway in said cylinder means that communicates between said bore and the exterior of said cylinder means, the location of said further exit passageway being such that when said detent resides substantially in said recess in said cam means, that annular chamber that communicates with said exit location of said passageway in said piston means is in communication with said further exit passageway in said cylinder means.
 6. The improvement of claim 5 wherein said stitching machine includes a work support hingedly mounted thereon for movement between positions of engagement and nonengagement with a workpiece, said work support being biased toward its position of engagement with said workpiece, and including a pneumatically activated piston-cylinder means whose piston member is connected to said work support and whose cylinder means is connected in fluid communication with said further exit passageway in said cylinder means whereby when said detent resides substantially in said recess in said cam means, pressurized fluid flows to said cylinder means to move said piston means therein and move said work support to its position of nonengagement with said workpiece.
 7. The improvement of claim 2 wherein said passageway in said piston means has a cross-sectional area that is smaller than the remainder of the cross-sectional area of that end of said piston means that is exposed to said pneumatic pressure whereby the force exerted against said exposed end of said piston means is sufficient to overcome said bias of said piston means and further provide for the flow of pressurized fluid through said passageway to operate said positioning motor.
 8. The improvement of claim 1 wherein said passageway in said piston means includes a plurality of exit ports, each of which is of a smaller cross-sectional area than the minimum cross-sectional area of said passageway, and the total of the cross-sectional areas of all of said exit ports is greater than said minimum cross-sectional area of said passageway.
 9. The improvement of claim 1 wherein said passageway in said piston means includes a portion which extends substantially axially along the length of said piston means and a portion which extends substantially laterally from said axial portion and which exits into said bore of said cylinder means.
 10. The improvement of claim 1 wherein that end of said piston means disposed adjacent said cam means is provided with a tip member adapted to enhance the functioning of said end as a detent means.
 11. The improvement of claim 1 and including thread cutter means including a piston and cylinder means, knife means mounted on the free end of said piston in position to cut the thread employed with said stitching machine upon actuation of said piston means, conduit means connecting said cylinder means in fluid communication with said further exit passageway from said control cylinder whereby when said detent means resides substantially within said recess in said cam means, said piston is activated to cut said thread.
 12. The improvement of claim 11 and including time delay flow control means interposed in said conduit between said control cylinder and said thread cutter cylinder means.
 13. In a stitching machine including a needle adapted for reciprocatory movement into and out of a workpiece, shaft means connected to said needle for reciprocating said needle upon rotation of said shaft, drive means including a drive motor for rotating said shaft, operator control means for activating and deactivating said drive means, the improvement for positioning said needle in a preselected position along its reciprocatory path comprising pulley means includinG overriding clutch means fitted on said shaft means, a pneumatically powered positioning motor, loop means drivingly connecting said positioning motor to said pulley means for rotating said shaft upon activation of said positioning motor, cam means disposed on said shaft and rotatable therewith, said cam means including a recess therein, pneumatically actuable reciprocatory piston means having one of its ends disposed adjacent said cam means and defining detent means adapted to move between positions of engagement and nonengagement with said cam means, said piston means being biased toward a position of nonengagement of said detent means with said cam means, cylinder means including bore means adapted to receive said piston means therein for reciprocatory movement of said piston means, a source of pressurized fluid, conduit means connecting said source of pressurized fluid to one end of said bore means for supplying pneumatic pressure to one end of said piston means to urge said piston means toward a position of engagement of said detent means with said cam means, means defining a passageway for the flow of pressurized fluid along said piston means from said one end thereof that is exposed to said pneumatic pressure to said bore in said housing, a plurality of seal means encircling said piston means on opposite sides of the exit end of said passageway along said piston means and sealing the annular space between said piston and the internal wall of said bore on opposite sides of said exit end of said passageway to define a first annular chamber, further seal means encircling said piston means and sealing the annular space between said piston and said bore at a location more near that end of the piston that is exposed to said pneumatic pressure than either of said plurality of seal means and spaced therefrom to define a further annular chamber between said further seal means and the neighboring one of said plurality of seal means, means defining a lateral passageway in said cylinder means and communicating between said bore and the exterior of said cylinder means, conduit means connecting said lateral passageway in said cylinder means to said positioning motor for conveying pressurized fluid to said motor for operation thereof, normally closed valve means interposed in said conduit means connecting said source of pressurized fluid to said cylinder means whereby upon the opening of said valve means pressurized fluid is admitted to said one end of said cylinder means to move said piston means within said bore and cause said detent means to engage said cam means and to admit pressurized fluid to said first chamber, thence to said positioning motor for rotating said drive shaft and said cam means mounted thereon, whereby said detent means substantially enters said recess in said cam and said piston moves within said bore by an amount sufficient to close off the flow of air to said positioning motor to stop the same. 